/**
 * This file is part of 1genia trampoline
 * Copyright (C) 2007 1genia (contact@1genia.com)
 *
 * This library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; version 3 of the License. 
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details. 
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; see the file COPYING.TXT.  If not,
 * write to the Free Software Foundation, Inc., 51 Franklin Street,
 * Fifth Floor, Boston, MA 02110-1301, USA. 
 **/
package com.genia.toolbox.web.gwt.form.client.widget.item;

import com.genia.toolbox.web.gwt.basics.client.i18n.GwtI18nMessage;
import com.genia.toolbox.web.gwt.form.client.form.Item;
import com.genia.toolbox.web.gwt.form.client.validator.ValidatorCallback;

/**
 * this interface represents the widget associated to an Item from a Form. It
 * allows to display the validation errors to the user.
 */
public interface ItemWidget
{

  /**
   * return the {@link Item} this object represents.
   * 
   * @return the {@link Item} this object represents
   */
  public Item getItem();



  /**
   * add a listener that is called each time the value of this object change.
   * 
   * @param modifyListener
   *          the callback
   */
  public void addModifyListener(ItemWidgetModifyListener modifyListener);



  /**
   * Display or hide the error message associated to this item. If message is
   * <code>null</code> and an error message is currently displayed, the message
   * is hidden. Otherwise, if message is not null, it is displayed as an error
   * message.
   * 
   * @param message
   *          the message to display, or <code>null</code> to hide the error.
   */
  public void setErrorMessage(GwtI18nMessage message);



  /**
   * validate that the values are acceptable.
   * 
   * @param callback
   *          the callback that is called once the validation is done
   */
  public void validate(ValidatorCallback callback);

}
